MUC3是具重要生物学功能的膜结合型粘蛋白，我们发现MUC3羧基端翻译后经历SEA组件自酶切，而自酶切介导了MUC3调控结肠癌细胞EMT，但其分子机制不清。我们基于前期研究，提出MUC3羧基端SEA组件自酶切介导MUC3通过SEA组件侧翼EGF样结构域与EGFR家族的ErBb2结合并使其磷酸化，激活Wnt信号，调控EMT靶基因表达进而启动EMT的假说。本研究拟在细胞水平和动物模型水平，用不同酪氨酸位点磷酸化ErbB2抗体和免疫共沉淀实验证实MUC3通过EGF样结构域致ErbB2磷酸化，激光共聚焦、免疫印迹等检测Wnt信号相关蛋白证实ErbB2磷酸化激活Wnt信号，转录调控实验证实核转位的β-catenin调节EMT靶基因表达从而启动EMT。本课题揭示MUC3羧基端 SEA组件自酶切生物学意义及其介导MUC3调控结肠癌细胞EMT的分子机制，对认识MUC3的生物学功能和结肠癌发生机制具理论意义

MUC3 is a typical membrane-tethered mucin expressed in gastrointestinal tract and epithelial cancers, which exerts a pivotal biological role, including cell signalling, cell proliferation and tumour progression or cell polarity. We have found that the carboxyl-terminal domain of MUC3 is posttranslationally autoproteolysed at the SEA module. The autoproteolysis at the SEA module of human MUC3 carboxyl-terminal domain modulates its functional composition, for example, regulating the epithelial-mesenchymal transition (EMT) in colon cancer cells, but the mechanism is largely unknown. Based on the our previous study, we postulate that the autoproteolysis at the SEA module of human MUC3 carboxyl-terminal domain leads to the interaction between the epithermal growth factor(EGF)-like motif flanked beside SEA module and ErBb2, one of the members of EGF receptor(EGFR), and further phosphorylation of ErBb2 at the different tyrosine sites, the phosphorylated ErBb2 leads to the activation of Wnt/β-cateinin siganaling, the translocated β-cateinin transcriptionally regulated the genes involved in EMT of colon cancer cells, and finally induced the occurrence of EMT. The study is planed to confirm the interaction between the EGF-like motif flanked beside SEA module and ErBb2, one of the members of EGFR, and further phosphorylation of ErBb2 at the different tyrosine sites due to the autoproteolysis at the SEA module of human MUC3 carboxyl-terminal domain using the specific antibodies for detecting different tyrosine phosphorylated ErBb2 and Western blotting, the quantitation of the expression levels of different Wnt signaling cascade (protein and mRNA) is used to confirm the activation of Wnt signaling cascade due to MUC3 Self-cleavage induced phosphorylated ErBb2, the transcriptional regulation of EMT-related genes by translocated β-cateinin is studied by the traditionally transcriptional regulation experiments, thus, to determine the molecular mechanism(s) of MUC3 Self-cleavage induced EMT occurrence in colon cancer cells. Hence, we will reveal the exact molecular mechanism underlying autoproteolysis modulating the biological behaviour of colon cancer cells, and thus offer an important clue for the understanding of colon cancer carcinogenesis.